The incident took place on New Year's Eve, and many migrants admitted they expected security to be lax during the first night of 2019 due to celebrations.

RT reports: However, it turned out not to be the case: as the migrants prepared to climb the fence, US Customs and Border Protection agents retaliated with tear gas and arrested 25 people, including two teenagers.

In its statement following the incident, CBP said that the volleys were not aimed at migrants attempting the crossing, but at rock-throwers who prevented the agents from helping the children being dropped over the border fence.

"Border Patrol agents witnessed members of the group attempt to lift toddler sized children up and over the concertina wire and having difficulty accomplishing the task in a safe manner."

"Agents were not in a position to safely assist the children due to a large number of rocks being thrown at them."

The border patrol said they dispersed "smoke, pepper spray, and CS gas to a position upwind of the rock throwers."

CBP argued that none of the crossing migrants, including children, suffered from the effects of the gas, as the targeted perpetrators stood further away from the fence.

"The deployments were not directed at the migrants attempting entry on the US side or at the fence line," the agency insisted.

Department of Homeland Security spokesperson Katie Waldman accused "a violent mob of migrants" of "attacking" the border patrol force with "projectiles," saying the agents used "the minimum force necessary" to thwart the attack on the border and defend themselves. CBP estimated that about 150 migrants attempted to sneak into the US illegally.

However, several media outlets, including AP and Reuters, contradicted the version of events presented by the US officials.

A witness cited by Reuters said he did not observe any rocks being hurled at the agents, but saw a migrant being hit by an object that looked like a gas canister.

AP, citing its photographer at the scene, reported that the rocks were launched at the border agents by migrants only after they were pelted with tear gas.

AP reported that, contrary to CBP's report, some of the canisters did hurt the migrants, women, and children among them.

The last time the US border patrol resorted to tear gas to fend off an avalanche of migrants trying to break through the fence in November, it sparked a massive backlash after videos and photos of women and children as young as three coughing and fleeing in disarray went viral.

Waldman, however, used the incident on January 1 to prop up US President Donald Trump's idea of a $5bn border fence on the border with Mexico.

"Congress needs to fully fund the border wall, amend the TVPRA, and end the Flores Settlement Agreement that encourages and rewards this type of lawlessness by migrants at the border," Waldman said.

Trump has refused to back down on his border wall project, despite it being the cause of a partial government shutdown that has continued into its 11th day.

Trump instead accused Democrats of "not caring" about US security and inviting "all the crimes and drugs that Open Borders bring!"

With little time left until the Democrats officially take over the House of Representatives on Thursday, Trump reportedly called for a border security briefing at the White House on Wednesday